# File lib/phusion_passenger/abstract_server_collection.rb, line 260
        def cleanup
                must_not_be_in_synchronize_block
                @cleanup_lock.synchronize do
                        return if @done
                        @lock.synchronize do
                                @done = true
                                @cond.signal
                        end
                        @cleaner_thread.join
                        synchronize do
                                clear
                        end
                end
        end